Update - Problem happened again and this time I rode with the dealer's technician and this time we were able to duplicate the problem. He thinks it's a wiring issue. I am going to take it in next week and leave it.mannami said:My G6 developed a speedometer problem last week. At speeds above 75mph the needle would suddenly drop from 75 to 40 and then recover. Took it to the dealer this morning and while they couldn't duplicate the problem, they "re-programmed" the instrument cluster. I took it back out an went about 10 miles at 75mph and it seemed OK. Will have to watch it.